it might be the angle, but it(the caliper) looks cocked. no telling how that could happen, as i am sure you were very careful of the strike angles. I would loosen the bolts and see if you can get the caliper free. the suggestion to open the bleeder is a good one, but i can just see how teaching you to bleed the air out is going to go
sure was nice to see all the care you took in cleaning up the parts before you started the job and hammered them back together.